1. Field of the Invention
The present invention relates to outlet gate assemblies for railway hopper cars of the type allowing gravity, vacuum and pneumatic sled discharge of the bulk lading.
2. Description of the Prior Art
Hopper-type railway cars are used to transport lading which is discharged through outlet gate assemblies mounted at the bottoms of the cars. Bulk lading transported by hopper cars include finely divided materials such as sugar, flour, wheat, potash and cement. The filled hopper cars are delivered to shippers"" terminals for unloading.
Conventional methods used to unload hopper cars include gravity discharge, vacuum discharge and pneumatic sled discharge of lading. During gravity discharge, lading falls by gravity through a discharge opening in an outlet gate assembly. During vacuum discharge, lading falls down from the car through an outlet gate and into a closed discharge chute. A vacuum hose is connected to the discharge chute and vacuum is applied to the hose. Air drawn into the discharge chute carries the lading along the discharge chute and into the vacuum hose. During pneumatic sled discharge, a pneumatic sled is attached to the bottom of the discharge opening. The pneumatic sled includes screw-type conveyors for discharging lading from the hopper car. Compressed air is blown into the discharge opening to pressurize the inside of the hopper car and separate compacted lading. The lading falls through the discharge opening and into the screw conveyors for removal.
Each unloading method requires its own specialized equipment to unload a hopper car. Nonetheless, a shipper may require one unloading method over another. Typically, a shipper""s terminal can accommodate only one method for unloading a hopper car. For instance, one shipper may gravity discharge sugar from a hopper car while another shipper may vacuum discharge sugar from a hopper car. As a result, shipper requirements dictate the type of hopper car used to transport lading to discharge terminals.
To provide flexibility to the railroads, conventional outlet gate assemblies permit gravity discharge, vacuum discharge or pneumatic sled discharge. The same hopper car can accommodate all shippers without regard to the particular discharge method required. This flexibility gives the railroads increased freedom in scheduling hopper cars, particularly for seasonal loads, and reduces operating costs.
The prior art multi-discharge outlet gate assemblies include a rectangular frame that defines a rectangular discharge opening at the bottom of the assembly. A pair of opposed vacuum nozzles are mounted on the frame and open into the discharge opening. The opposed vacuum nozzles are centered on the transverse center plane of the discharge opening. Openings for the vacuum nozzles in the frame are covered by nozzle baffles. Upper and lower door slides are mounted in the frame. Each door slide is supported on its edges by the frame and extends through a slot in the frame. Slot seals prevent exposure of lading to outside contaminants. The gates are movable between closed and opened positions to open and close the upper and lower ends of the assembly.
In the prior art, an opening and closing drive shifts the upper gate between open and closed positions. The drive includes fixed racks and an operating shaft. The operating shaft carries pinions which engage the racks. The operating shaft is rotated in an appropriate direction to move the upper gate and the operating shaft in a desired direction.
In the prior art, a locking mechanism allows the upper gate to be locked to the lower gate so that both gates move together. When the gates are locked together, rotation of the operating shaft simultaneously moves both the upper and lower gates between opened and closed positions. When the gates are unlocked from one another, rotation of the operating shaft moves the upper gate only and the lower gate is stationary.
During gravity or pneumatic sled discharge of lading in the prior art, the door locking mechanism locks the upper and lower gates together. The operating shaft is rotated to move the upper and lower gates simultaneously from the closed position to the open position. Lading falls down through the gate assembly.
During vacuum discharge of the hopper car in the prior art, vacuum hoses are attached to the vacuum nozzles. The door locking mechanism is unlocked. The operating shaft is rotated to open the upper gate only. The lower gate remains closed. Lading falls down into the frame but cannot exit through the bottom of the assembly. Vacuum draws air and lading into the vacuum hoses.
Some prior art outlet gates include separate mud plates that are mounted to the frame below the lower discharge gate. These mud plates cover and protect structures above them, and are removable for gravity and pneumatic sled discharge.
In one aspect, the present invention provides an outlet gate assembly adapted to be mounted on a hopper-type container. The outlet gate assembly comprises a frame, an upper gate assembly and a lower gate assembly. The frame defines a generally rectangular discharge opening. The upper gate assembly is mounted on the frame and includes an upper plate having top and bottom surfaces and an upper rack that is mounted on the bottom surface of the plate. The lower gate assembly is also mounted on the frame and includes a lower plate having top and bottom surfaces and a rack mounted on the top surface of the plate. The outlet gate assembly also includes an upper shaft rotatably mounted on the frame and an upper pinion on the upper shaft and engaging the upper rack. The outlet gate assembly includes a lower shaft rotatably mounted on the frame and a lower pinion on the lower shaft and engaging the lower rack. The upper plate is movable between open and closed positions by rotating the upper shaft. The lower plate is movable between open and closed positions by rotating the lower shaft. The outlet gate assembly has a cavity below the bottom surface of the upper plate of the upper gate assembly and above at least part of the top surface of the lower gate assembly when the upper and lower plates are in the closed positions. At least part of the upper rack is within the cavity when the upper plate is in the closed position. All of the lower rack is outside of the cavity when the lower plate is in the closed position and when the lower plate is in the open position.
In another aspect, the present invention provides an outlet gate assembly adapted to be mounted on a hopper-type container. The assembly comprises a frame defining a generally rectangular discharge opening. An upper gate assembly is mounted on the frame at the discharge opening. The upper gate assembly includes an upper plate having top and bottom surfaces and a rack. A lower gate assembly is also mounted on the frame. The lower gate assembly includes a lower plate having top and bottom surfaces. An upper shaft is rotatably mounted on the frame. An upper pinion is on the upper shaft and engages the rack of the upper gate assembly. The upper plate is movable between open and closed positions by rotating the upper shaft. The lower plate is movable between open and closed positions. The outlet gate assembly has a cavity below the bottom surface of the upper plate of the upper gate assembly and above at least part of the top surface of the lower gate assembly when the upper and lower plates are in the closed positions. A vacuum discharge opening is between the level of the upper plate and the level of the lower plate and is positioned to provide an outlet from the cavity. The rectangular discharge opening of the frame has a transverse center plane that intersects the rack of the upper gate assembly when the upper plate is in the closed position. The vacuum discharge is offset from the transverse center plane of the rectangular discharge opening of the frame.
In another aspect, the present invention provides an outlet gate assembly adapted to be mounted on a hopper-type container. The assembly comprises a frame defining a generally rectangular discharge opening. The frame has a pair of frame side members and a transverse member extending between the side members. An upper gate assembly is mounted on the frame. The upper gate assembly includes an upper plate having top and bottom surfaces. A lower gate assembly is mounted on the frame. The lower gate assembly includes a lower plate having top and bottom surfaces. The upper plate is movable in a longitudinal direction between open and closed positions. The lower plate is movable in a longitudinal direction between open and closed positions. The outlet gate assembly has a cavity below the bottom surface of the upper plate of the upper gate assembly and above at least part of the top surface of the lower gate assembly when the upper and lower plates are in the closed positions. There is a seal between the transverse member of the frame and the bottom surface of the upper plate. The seal extends transversely across at least part of the upper plate. There is an ultra high molecular weight seal between the transverse member of the frame and the top surface of the lower plate. The ultra high molecular weight seal extends transversely across at least part of the lower plate. An ultra high molecular weight seal is between another portion of the frame and the top surface of the lower plate; this ultra high molecular weight seal extends transversely across at least part of the lower plate.
In another aspect, the present invention provides an outlet gate assembly adapted to be mounted on a hopper-type container. The outlet gate assembly comprises a frame defining a generally rectangular discharge opening. The frame has a pair of frame side members and a rear frame member. An upper gate assembly is mounted on the frame and is movable longitudinally between open and closed positions. The upper gate assembly includes an upper plate with a top surface and a bottom surface. A lower gate assembly is also mounted on the frame and is movable longitudinally between open and closed positions. The lower gate assembly includes a lower plate with a top surface and a bottom surface. The outlet gate assembly has a cavity below the bottom surface of the upper plate of the upper gate assembly and above at least part of the top surface of the lower plate of the lower gate assembly when the upper and lower plates are in the closed positions. The frame side members have a plurality of longitudinal horizontal surfaces below the cavity that are exposed when the upper gate assembly and lower gate assembly are in the open position. These longitudinal horizontal surfaces are covered by a portion of the lower gate assembly when the lower gate assembly is in the closed position. The outlet gate assembly includes one horizontal transverse surface below the cavity that is exposed when the upper gate assembly and the lower gate assembly are in the open position and covered by a portion of the lower gate assembly when the lower gate assembly is in the closed position.